From production centers such broadband signals arrive at a TV service centre, from which they are sent to a broadband exchange, after their conversion into a form suitable for switching and transmission. The transmission is carried out by a suitable system utilizing optical cables, coaxial cables or radio links, in order to reach the subscriber; the subscribers are, of course, equipped with decoders able to reconstruct the original TV signal.
Beside the transmission system between the broadband exchange and the subscriber's house, transmission systems exist between the service centers and the switching exchange, at the exchange and at the subscriber's location.
A problem to be solved when implementing a broadband broadcasting system, using already available apparatus which operates according to interface specifications recommended by CCITT, is the large number of interfacing circuits, generally different from one another, necessary to effect the numerous transmission code conversions the broadband signals have to undergo, according to their hierarchical levels.
In particular, conversions are required at the service centers output, at the input and output both of the broadband exchange and of long-and-short distance transmission systems, and at the subscriber's location.
Such a problem is described in the paper entitled "Architectural and technology aspects of broadband switching", presented by H. Bauch and others at ISS '84 Conference, held in Florence, 7-11 May 1984, and issued in the proceedings at session 23 C, Paper 1. More particularly, in the second paragraph of the second column on page 2, the necessity is mentioned of generating a limited redundancy code as close as possible to the source, where the transmission rate is lower.